Have you noticed the yogurt section in your grocery store lately? It is being taken over by Greek yogurt! In my grocery store over half of the space allotted for yogurt now has the Greek variety. So what makes Greek yogurt Greek? How is it different and why?

What is Greek yogurt?

Greek yogurt is really strained yogurt, popular in Eastern Mediterranean, Near East, and South Asia countries. It is called Greek in the U.S. because that is what the company Fage marketed their product as. Fage is a yogurt company which originated in Greece and was one of the first companies to sell Greek yogurt in the U.S. Naming their thicker and creamier yogurt “Greek” was a clever marketing strategy. “Greek” sounds foreign, sophisticated, and interesting. “Strained” brings to mind less pleasant thoughts.

What is the point of straining yogurt? Straining removes some of the whey. Whey is the watery liquid from milk. It used to be known primarily as a byproduct of making cheese, but is now recognized as a great source of protein. Less whey means a thicker yogurt. Strained yogurt also has more protein because there is less water to dilute it. The properties of Greek yogurt can be mimicked through other processes or by adding thickeners. These non-traditional methods can have some benefits, they may lower the fat content or decrease syneresis in the yogurt.

Syneresis is the separation of liquid from solid. For example, there is often a film of water on the top of sour cream that has to be stirred in.

No matter how the yogurt is made, Greek yogurt is thicker and creamier than regular yogurt. If you haven’t tried it yet, I highly recommend that you do. Yogurt isn’t my favorite dairy food, but I’ve liked the Greek varieties I’ve tried.

So…what is yogurt?

Yogurt has been around for ages. It is a fermented milk product that was probably a happy discovery, not a planned invention. Think of it as curdled milk with a twist. Instead of microorganisms spoiling good milk into something smelly and inedible, in yogurt the microorganisms ferment the milk into something quite tasty. The difference is due to which microorganisms are present. Yogurt is only created by specific bacteria which thrive in specific conditions. A basic yogurt recipe includes several steps that help make the yogurt-creating bacteria comfortable.

1. Heat the milk to approximately 185°F (85°C), make sure not to scorch the milk. This kills off most of the bacteria within the milk. With the other bacteria gone, the bacteria starter culture  has no competition for resources.
2. Cool the milk down to roughly 110°F (43°C) and add the bacteria starter culture. This is a great temperature for thermophilic (heat loving) bacteria. A little bit of plain yogurt can be used as the starter since it contains all the needed bacteria. There are serveral strands of bacteria used in yogurt. The most common are Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillus acidophilus.
3. Keep the milk/bacteria mix warm, around 100°F (38°C), for several hours as it becomes yogurt. During the incubation period the bacteria grow, multiply, and ferment lactose into lactic acid. The longer the yogurt sits the more lactic acid is produced and the more tart the yogurt becomes.

The lactic acid also plays a key role in the texture of yogurt as well. Lactic acid lowers the pH of milk. In the more acidic environment some of the proteins, called caseins, denature and start to clump together. This is called coagulatation. Remember the nursury rhyme “Little Miss Muffet”? Her curds and whey refer to milk that has separated into solid clumps(curds) and the left over liquid(whey). In yogurt, the milk doesn’t form distinct curds but it does thicken noticeably.

So with the right conditions and right bacteria, milk can be turned into yogurt. And with an additional step, yogurt can become Greek, or strained, yogurt. What a great progression!

Photo: Christian Kitazume

Sources:

• Modern Food Microbiology, 7th Edition, by James M. Jay, Martin J. Loessner, and David A. Golden
• “Greek-Style Homemade Yogurt” by Fernando González del Cueto
• “Homemade Yogurt Recipe” from Martha Stuart Living
• “How to Make Yogurt” edited by Mari Bun, Krystle C, Travis Derouin, Jack Herrick and 95 others on Wiki How.
• “My Big, Thick Greek Yogurt” by Jeff Gelski on Food Business News